Many biological processes and metabolic functions of individual cell types are particularly difficult to study in vivo due to the vast array of different cells communicating between each other. Further, in many cases technical as well as ethical considerations do not allow in vivo experimentation. Therefore, in vitro cell culture systems have been developed to allow to specific study of individual cell types and cell types particularly difficult to study in vivo, such as cells derived from human tissue. The most common cell culture systems use a two dimensional surface such as plastic or glass to grow cells upon. They provide a highly artificial cell culture environment where cells are forced to grow in ways they never do in the body.
There is a growing recognition of the disadvantages of the conventional in vitro cell culture systems, namely the lack of an adequate preservation of the biological functions and complexity present in vivo.
In order for a cell to receive correct signals for proliferation, differentiation, migration or programmed cell death, the spatial cues and topologically defined position of specific cell membrane receptors, attachment molecules or release of humoral factors are essential. These signal transduction pathways are stimulated and influenced by the organization and structure of the cell cytoskeleton. The architecture of which is comprised of and defined by a vast array of cell-cell and cell-matrix contacts, as well as cytoskeleton-receptor structure. All of these cell function-determining factors are highly altered in conventional two dimensional cell culture systems due to the altered cell shape and cell cytoskeleton morphology, which lead to aberrant cytoskeletal compositions.
Hence in recent years, research has become more and more focused on cell culture systems, which would mimic the three dimensional environments found in vivo.
A number of approaches to establish three dimensional cell culture systems have been undertaken with the major aim to mimic the extracellular matrix (ECM) and configuration and to give structural, dimensional stability to the cells in culture.
Recent work has demonstrated the major influence and importance of unique micro- and nano-environments in spatial organization of tissue like patterns of cells and their signal transduction as well as differentiation functions (Mueller-Klieser 1997; Cukierman, Pankov et al. 2001; Walpita and Hay 2002).
Amongst the most predominant culture methods are gel and collagen systems, nanofiber scaffolds and porous scaffolds that aim to promote three dimensional cell growth (for review see Lee, Cuddihy et al. 2008). All of these platforms developed to date, however, have distinct disadvantages such as cell aggregation, low cell survival or experimental limitations.
Only few attempts have been made to develop functional three dimensional cell culture systems using fiber scaffolds. These scaffolds generally consist of a fibrous structure. The benefits of such three dimensional fibrous matrices include a high surface-to-volume ratio and a structure similar to the in vivo collagen and elastin network. So far, there is only one product commercially available, which offers a three dimensional platform constructed of nanofiber scaffolds (Celltreat™). These fibers, however, come aligned in well defined spatial distribution and without treatment of the fiber surface such as coating with extracellular matrix molecules.
Fiber alignment appears to have very specific effects on cell cultures, mainly on migration and morphology, which are not desired in the present invention.
US patent US20070269481 describes a ‘Biomemetic Scaffold’ consisting of aligned nanofibers with or without crosslinked coating of the fibers. However, the alignment is not desired for many cell culture systems.
Further US patent US20060263417 describes ‘Electrospun blends of natural and synthetic polymer fibers as tissue engineering scaffolds’. Similarly, U.S. Pat. No. 7,704,740 ‘Nanofibrillar structure and applications including cell and tissue culture’ describes the manufacturing of random oriented electrospun nanofibers with the aim to proliferate cell and tissue cultures.